	html{
		overflow-x:hidden;
		overflow-y:hidden;
	}
	
	body{
		text-align:center;
		/* height:500px; */
	}
	
	div#div_bg{
		background-repeat:no-repeat;
		background-attachment: fixed;
		position:absolute;
		background:#00FF00 url(../image/bg.jpg);
		z-index: -1;
		width: 100%;
		height: 100%;
		top: 0px;
		left: 0px;
	}
	.bottom_div{
		heigt=50px;
		margin-left=50%;
		opacity:0.5;
		filter:alpha(opacity=50); 
		bottom:0;
		left:0;
		right:0;
		position:fixed;
		background:#fff;
	}
	div#bg_music_btn{
		background-color: rgba(120,220,210,.7);
		height: 20px;width: 100px;
		right: 10px;top:10px;
		position: absolute;
	}
	div#user_name{
		color:#ffffff;
		left: 10px;top:10px;
		position: absolute;
	}